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Mechanical modeling of granite subjected to contact loading
KTH, School of Engineering Sciences (SCI), Solid Mechanics (Dept.), Solid Mechanics (Div.).
2019 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The mechanical properties of Bohus granite subjected to contact loading is investigated based on experimental and numerical results. An elasto-plastic constitutive material model combined with a damage description is employed. The material model parameters are determined based on experimental results. Any kind of inelastic deformation except the tensile failure is described by a linear Drucker-Prager (DP) plasticity model with variable dilation angle. As for the damage description, an anisotropic damage model (DFH model) is considered to account for the tensile failure (i.e. mode I fracture). The resulting constitutive model is implemented numerically to simulate the mechanical behavior of the material under indentation loading up to its load capacity.  In paper A, the DP material model parameters are calibrated based on quasioedometric tests performed in an earlier work. It is described how the yield surface and dilation angle are determined from this test. The calibrated material model is implemented numerically in a commercial finite element software. The numerical model is validated based on quasi-static spherical indentation tests performed in this work. The force-penetration (P-h) response of the material is recorded during the indentation tests. Moreover, a high speed camera is utilized to observe the specimen surface around the contact area during the indentation test. It is detected that the observed load-drops in the P-h response correspond to material removals on the specimen surface. The tested specimens are also scanned by X-ray tomography to investigate the fracture pattern.   In paper B, the anisotropic DFH damage model is employed in order to predict the fracture pattern observed in the indentation test. The chosen damage model considers the heterogeneity in the material tensile strength. It is described how the statistical distribution of the tensile strength is calibrated. The calibrated DFH model is combined with the DP model and the resulting DP-DFH model is utilized to simulate the P-h response and the fragmentation process of Bohus granite subjected to quasi-static contact loading.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2019.
Series
TRITA-SCI-FOU ; 2019:51
National Category
Applied Mechanics
Research subject
Solid Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-263592ISBN: 978-91-7873-363-7 (print)OAI: oai:DiVA.org:kth-263592DiVA, id: diva2:1368350
Presentation
2019-11-29, Seminarierummet Hållfasthetslära, Teknikringen 8D, KTH, Stockholm, 10:15 (English)
Opponent
Supervisors
Note

Examinator: Professor Mårten Olsson, KTH, Stockholm

QC 20191108

Available from: 2019-11-08 Created: 2019-11-06 Last updated: 2019-11-08Bibliographically approved
List of papers
1. On the Inelastic Mechanical Behavior of Granite: Study Based on Quasi-oedometric and Indentation Tests
Open this publication in new window or tab >>On the Inelastic Mechanical Behavior of Granite: Study Based on Quasi-oedometric and Indentation Tests
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2019 (English)In: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 52, no 3, p. 645-657Article in journal (Refereed) Published
Abstract [en]

The inelastic behavior of Bohus granite is investigated based on experimental and numerical results. The yield surface and related dilation angle are determined based on quasi-oedometric tests performed in an earlier work. It is shown how to obtain the yield surface and dilation angle from this test for hydrostatic pressure levels up to 750MPa. In the constitutive modeling, a Drucker-Prager law is employed together with a variable dilation angle. The constitutive model is first applied to simulate the quasi-oedometric test and the stress and strain fields are obtained. Furthermore, the validation of the model is investigated by simulation of the spherical indentation test. The results are compared with corresponding experimental data and a good agreement is found.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Quasi-static indentation, Granite, Inelastic behavior, Tomography
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-248087 (URN)10.1007/s00603-018-1646-3 (DOI)000460704000001 ()2-s2.0-85056638291 (Scopus ID)
Note

QC 20190429

Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2019-11-07Bibliographically approved
2. A damage model for granite subjected to quasi-static contact loading
Open this publication in new window or tab >>A damage model for granite subjected to quasi-static contact loading
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2019 (English)Report (Other academic)
National Category
Mechanical Engineering Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-263587 (URN)
Note

QC 20191113

Available from: 2019-11-06 Created: 2019-11-06 Last updated: 2019-11-13Bibliographically approved

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